Cabin Pressure Control Systems (CPCSs) commonly include an outflow valve, such as a multi-door outflow valve, which is modulated during flight to maintain cabin air pressure within a desired range. The multi-door outflow valve may include, for example, a frame, a first door (e.g., a first rectangular butterfly plate) pivotally mounted to a first portion of the frame, and a second door (e.g., a second rectangular butterfly plate) pivotally mounted to a second portion of the frame. The multi-door outflow valve may be mounted in the aircraft fuselage such that the first door is closer to the tail of the aircraft than is the second door; for this reason, the first door and the second door may be referred to as the “aft door” and the “forward door,” respectively. The aft and forward doors may be mechanically linked by one or more linkages and move in unison between a closed position and a partially open or “cruise” position. In the closed position, the aft and forward doors sealingly engage one another and an inner periphery of the frame to generally prevent pressurized air from escaping the fuselage. In the cruise position, the aft and forward doors permit pressurized airflow from the aircraft's fuselage to the aircraft's external environment (referred to herein as “ambient.”) The outflow valve may also be positioned to provide additional forward thrust to the aircraft when in the cruise position (commonly referred to as “thrust recovery”).
It has been found that, by affixing a curved or cylindrical bellmouth to the inner end of the aft door, the likelihood of development of downstream vortices can be decreased under cruise conditions to lessen the production of acoustic tones. However, as conventionally designed and implemented, the addition of an aft door bellmouth has certain limitations. First, vortices can still develop when the outflow valve is in the cruise position, which may result in the production of undesirable tonal noises. More significantly, the addition of an aft door bellmouth can greatly increase the rigidity of the aft door. Due to this increase in rigidity, the aft door may be hindered from deflecting in conjunction with the more-flexible forward door, which tends to deflect or bulge outward during pressure loading of the outflow valve. A sizable leakage gap can thus form between the aft door and the forward door in the closed position, and significant leakage can occur. Although a door-to-door seal (e.g., a polymeric strip) can be mounted to the aft door to reduce leakage through the outflow valve in the closed position, the addition of such a door-to-door seal increases part count, complexity, and overall cost of the outflow valve, and can decrease the thrust output of the outflow valve in the cruise position.
There thus exists an ongoing need to provide embodiments of an outflow valve suitable for deployment within a cabin pressure control system that overcomes the above-described limitations. In particular, it would be desirable to provide an outflow valve (e.g., a multi-door outflow valve) that includes a door-mounted bellmouth (e.g., an aft door bellmouth) and that provides quiet operation, relatively high thrust output in the cruise position, and low leakage in a closed position. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.